The current knowledge of the spatial variability of precipitation in High Mountain Asia is based on the remotely-sensed estimates (coarse spatial and temporal resolution) or data from sparsely-distributed rain gauges. However, as precipitation is strongly affected by topography in mountainous terrain, the spatially varying precipitation and the resulting water balances are currently poorly understood. To fill this gap in knowledge, we studied the spatial variation of the precipitation and its impact on water balance in a small headwater basin located in the foothills of the Himalaya, Nepal. We deployed ten rain gauges and climate stations, spanning the whole elevation range 700–4500 m above sea level (masl) for a period of four years. Our results show a quadratic polynomial relationship between annual precipitation and station elevation, which are used to produce annual precipitation maps. The performance of the elevation-based precipitation estimates is adequate in closing the water balance while the performances of average precipitation and Thiessen polygon method are poor and inconsistent in closing the water balance. We also demonstrate that precipitation estimates from one or two gauges at the lowest basin elevation substantially underestimate the water balance. However, the precipitation from one or two rain gauges at 2000–3000 masl provide a significantly better estimate of the water balance of a small headwater basin.

中文翻译：

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尼泊尔源头高山流域的空间变化降水及其对水平衡的影响

目前有关亚洲高山山区降水空间变异性的知识是基于遥感估算（粗略的空间和时间分辨率）或稀疏分布的雨量计的数据。但是，由于降水受山区地形的强烈影响，因此目前对空间变化的降水和由此产生的水平衡了解得很少。为了填补这一知识空白，我们研究了尼泊尔喜马拉雅山山麓小源头盆地降水的空间变化及其对水平衡的影响。我们部署了十个雨量计和气候站，为期四年，横跨海拔高度（masl）的整个海拔范围700-4500 m。我们的结果表明年降水量与站高之间存在二次多项式关系，用于产生年度降水图。基于海拔的降水估计的性能足以关闭水量平衡，而平均降水量和Thiessen多边形方法的性能很差，并且无法平衡水量平衡。我们还证明，在最低盆地高程处从一个或两个水位计得出的降水估计值大大低估了水平衡。但是，一个或两个雨量计在2000–3000 masl的降水量提供了一个较小的上游水源水平衡的明显更好的估计。基于海拔的降水估计的性能足以关闭水量平衡，而平均降水量和Thiessen多边形方法的性能很差，并且无法平衡水量平衡。我们还证明，在最低盆地高程处从一个或两个水位计得出的降水估计值大大低估了水平衡。但是，一个或两个雨量计在2000–3000 masl的降水量提供了一个较小的上游水源水平衡的明显更好的估计。基于海拔的降水估计的性能足以关闭水量平衡，而平均降水量和Thiessen多边形方法的性能很差，并且无法平衡水量平衡。我们还证明，在最低盆地高程处从一个或两个水位计得出的降水估计值大大低估了水平衡。但是，一个或两个雨量计在2000–3000 masl的降水量提供了一个较小的上游水源水平衡的明显更好的估计。